Smallpox. To the veteran or some aid workers, it means a shot and a scar on the upper arm. To some older folks, it is one of many things that was spoken of and discussed in medical circles years ago, but no longer. To the average person it is an ancient ailment that, like many ancient ailments, killed countless, faceless ancestors. It was yet another one of the many things that would take people’s’ lives back then, thankfully long gone now.

However, while smallpox is taken very seriously by those old enough to remember it, and those in medical circles, it is often underplayed by the public at large. The virus was so deadly that it undoubtedly changed the entire course of human history on more than one occasion. Sometimes the sheer numbers of lives that it took are not completely conveyed — in the 1900s alone, it killed an estimated 300 to 500 million people. Many argue that its eradication is one of the greatest medical victories in our history. Another could argue that the threat still exists.

Smallpox was declared eradicated in 1980.

Read the signs and symptoms of smallpox here.

The earliest cases of smallpox date back to ancient days — thousands of years ago, in ancient India, Egypt and China, there are reports that describe something very similar to smallpox. It spread throughout the world under different  names, and it was relentless. Over the course of two years in the 700s, it allegedly wiped out one-third of Japan’s entire population, though it didn’t spread to western Asia and Europe until much later.

These early cases are often disputed, as proof is obviously lacking when it comes to ancient medicine. This disease was so deadly, that a sure way of knowing whether or not it had spread to a country at any given date in history is to see whether or not the historians mentioned it. Many are certain that, if smallpox had spread to their country, they would undoubtedly write about it in great length, as the devastation would be unforgettable.

A man who has contracted small pox is shown with a formation of scar-producing pustules on his body on Nov. 1, 1941. To encourage the public to vaccinate against the highly contagious viral disease caused by a poxvirus, the New York State Board of Health anti-disease campaign is using this image in New York and other states with the caption, “This man was never vaccinated against smallpox.” (AP Photo)

One notable and infamous spread of the disease was to the Americas during westward European expansion. The sheer numbers of dead Native Americans from the smallpox virus is still not entirely grasped by many Americans today. Think of all the stories of battles between Native Americans and pioneers and settlers — the close calls, the overrun settlements on both sides, the incredible fight that many natives put up.

Now realize that, just prior to all of these battles and wars, smallpox had wiped out 90% of the population; a lot of it occurred so fast, that it outpaced the first contact in many cases. Entire swaths of people were getting wiped out and they hadn’t even seen or heard of a European at that point. The world of the those native to the Americas at the time would be easily post-apocalyptic by any standard, including the Aztec and especially the Incan populations. Smallpox actually incidentally (or intentionally) assisted the colonial efforts of Europe quite often, and not just in the Americas.